using System;

double calc(int min){

    double minPrice = 0;

    if(min>=30 && min<60){

        minPrice = 25/30.0;

    }else if(min>=60 && min<120){

        minPrice = 40/60.0;

    }else if (min>=120 && min<300){

        minPrice = 70/120.0;

    }else{

        minPrice = 140/300.0;

    }

    var totalPrice =  Math.Ceiling(minPrice * min);

    Console.WriteLine("Total Price :" + totalPrice); 

    Console.WriteLine(String.Format("{0} % 5 = {1}",totalPrice, (totalPrice % 5)));

    double reminder = 0;

        var modulus =totalPrice % 5;

    if(modulus>0){

        reminder = 5-modulus;

    }

    //var roundedTotal = totalPrice + (5-(totalPrice % 5));

    var roundedTotal = totalPrice + reminder;

    return roundedTotal;

}

​

Console.WriteLine(calc(150));